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利用配备高精度局部位移传感器的空心圆柱扭剪仪对杭州软黏土开展了系列应力旋转路径条件下的试验研究,包括:大主应力沿不同角度的定向剪切,不同剪应力水平下大主应力单纯连续旋转后定向剪切以及大主应力往复循环旋转后定向剪切3类典型应力路径,并考虑了中主应力系数及剪应力水平的影响。重点分析应力旋转路径对软黏土小应变刚度特性的影响。主要结论有:在不同的复杂应力条件下软黏土的刚度均受应变大小的影响,应变小于0.01%时软黏土的刚度很大,在0.01%~0.1%范围内刚度迅速衰减;在定向剪切条件下剪切方向对软黏土小应变剪切刚度的影响并不明显,而中主应力系数的影响比较显著;在主应力单纯旋转阶段软黏土会因不同的剪应力幅值产生不同程度的应变累积,继而对土体的小应变刚度的影响程度也不同;主应力往复循环旋转虽然也会产生前期累积应变,但土体在后期定向剪切阶段的初始刚度并未显著衰减,说明应力旋转模式对小应变刚度也有很大影响。
A series of experimental research on Hangzhou soft clay with a series of stress rotation paths was carried out by using a hollow cylindrical torsional shear instrument equipped with a high-precision local displacement sensor. The test includes the following aspects: directional shear of principal principal stress along different angles, principal stress at different levels of shear stress Three kinds of typical stress paths of directionally sheared directional shear after the simple continuous rotation and large principal stress reciprocating cycle rotation were taken into account, and the effects of the middle principal stress coefficient and the shear stress level were considered. The effect of stress rotation path on the small strain stiffness of soft clay is analyzed emphatically. The main conclusions are as follows: The stiffness of soft clay under different complex stress conditions is affected by the strain. When the strain is less than 0.01%, the stiffness of soft clay is very large and the stiffness decays rapidly in the range of 0.01% -0.1% The effect of shearing direction on the small shear stiffness of soft clay is not obvious, but the influence of middle principal stress coefficient is significant. In the simple rotation stage of main stress, the soft clay will produce different degrees of strain due to different shear stress amplitudes And then the effect on the small strain stiffness of the soil is also different. While the cyclic stress rotation of the principal stress will also produce the pre-cumulative strain, the initial stiffness of the soil in the late directional shear phase does not decay significantly, indicating that the stress rotation mode Small strain stiffness also has a great impact.